Annotation/Interface Conflict?

I've encountered strange behavior which I can't explain. I have a DAO class, defined as a normal Spring bean. I get an instance of it by caling ApplicationContext.getBean(). This worked fine until today, when I had the class implement a simple interface. Now I suddenly began getting class cast exceptions becaase the getBean() method returned an object of class $Proxy10 instead of the DAO class I had been expecting.

After some trial and error, I discovered the getBean() call returned the $Proxy10 object only when the class implemented the interface and had a method annotated as @Transactional. When I didn't implement the interface, or when I removed the @Transactional annotation, the getBean() method worked perfectly. But when I had both the interface implementation and the annotation, I got the dreaded $Proxy10 object.

I'm using Spring 2.5.6.

Anyone have any ideas what causes this?

You might want to have a read of the reference manual, there's some information on dynamic proxies which should help explain what you're seeing.
http://static.springsource.org/sprin...ve-annotations

Well, yes, I've read that more than once, but didn't see anything that describes this behavior. What specifically are you referring to that I'm missing?

So if you try and cast it to the interface it's going to work fine, if you cast it to the class you get a ClassCastException.

Quote:

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If the target object to be proxied implements at least one interface then a JDK dynamic proxy will be used. All of the interfaces implemented by the target type will be proxied. If the target object does not implement any interfaces then a CGLIB proxy will be created.

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So @Transactional means it's going to get proxied and then follow those rules. When you call getBean you aren't dealing with the raw type you are dealing with a proxy instead. If you remove the interface you're going to force it to proxy the class instead which uses a different kind of proxy hence the different behaviour.

http://static.springsource.org/sprin...l#aop-proxying
http://denis-zhdanov.blogspot.com/20...problem-2.html